Lutein-enriched emulsion-based delivery systems: Influence of pH and temperature on physical and chemical stability
Introduction
An important trend in the modern food industry is for products that are manufactured “without artificial additives” as preservatives, flavorings, and colorings (Sloan, 2015). In addition, consumers are tending to purchase more functional food products that claim to provide additional health benefits beyond their normal nutritional effects (Sloan, 2015). Lutein is a natural pigment that has been shown to exhibit a range of potentially beneficial biological effects, and it is therefore an interesting food ingredient for replacing artificial dyes and for creating functional foods. Indeed, it has recently been reported that lutein, which is mainly extracted from Marigold flowers (Tagetes erecta), has the fastest growing market among the carotenoids with a market value of around US$233 million in 2010, projected to grow to US$309 million by 2018 (Berman et al., 2015).
Like other carotenoids, lutein is one of the major pigments in fruits and vegetables that lead to their characteristic yellow, red and orange colors. These carotenoids are found in appreciable levels in green leafy vegetables such as kale, spinach, lettuce, broccoli, peas, Brussel sprouts, and parsley, as well as in egg yolks, tomatoes, corn, and marigold flowers (Abdel-Aal el et al., 2013, Boon et al., 2010, Krinsky et al., 2003, Sajilata et al., 2008). Lutein belongs to the xanthophyll class of carotenoids, which are oxygenated carotenes (Sajilata et al., 2008).
Lutein, as well as other xanthophylls, may decrease the risk of age-related macular degeneration and cataracts (Abdel-Aal el et al., 2013, Boon et al., 2010, Sajilata et al., 2008). Xanthophylls accumulate in the pigmented region of the human eye, which is called the macul, and since they have high absorptivity within a specific wavelength range, they absorb the blue light that reaches the eye. Moreover, they can act as antioxidants by scavenging free radicals or quenching singlet oxygen (Krinsky et al., 2003, Nagao, 2014, Sajilata et al., 2008), thus decreasing oxidative stress in the retina. Since carotenoids, including lutein, cannot be synthesized in the human body, it is essential that they be consumed as part of the daily diet (Khalil et al., 2012, Nagao, 2014, Sajilata et al., 2008). The Joint FAO/WHO Expert Committee on Food Additives (JECFA) concluded that the acceptable daily intake (ADI) for lutein and zeaxanthin is 0–2 mg/kg body weight (JECFA, 2005). In addition, 10 mg/day has been reported to be an effective dose for providing protection against diseases such as age-related macular degeneration and cataracts (Frede et al., 2014). Dosages of up to 40 mg/day in humans showed no adverse effects after eye examinations. The presence of lutein crystals that could cause retinal damage was also not observed. The only adverse effect was carotenedermia, which is a reversible and harmless cutaneous hyperpigmentation (Alves-Rodrigues & Shao, 2004). Eggs are one of the major natural sources for carotenoids and they also contain them in a very bioavailable form. However, there are some concerns about the consumption of eggs leading to increased serum cholesterol levels.
Another concern is that lutein is sensitive to the thermal processing and storage process and thus can degrade in foods that are naturally rich or enhanced with lutein (Alam, Ushiyama, & Aramaki, 2009). Carotenoid oxidation can be enhanced by photodegradation, thermal degradation, acid exposure, autoxidation, and singlet oxygen; these different pathways can cause bioactivity and quality (color loss and rancidity) loss in food products fortified with carotenoids (Boon et al., 2010, Sajilata et al., 2008). Therefore, it is crucial to understand the degradation process of lutein in order to develop better protection systems for them in foods (Boon et al., 2010).
One of the major challenges to utilizing lutein as a functional food ingredient is its relatively low and variable oral bioavailability (Khalil et al., 2012, Nagao, 2014, Sajilata et al., 2008). The poor bioavailability profile of lutein can be attributed to its low water-solubility, high melting-point, and poor chemical stability (Frede et al., 2014, McClements and Li, 2010). As a result of these challenges, carotenoids cannot usually be directly incorporated into aqueous-based foods. Instead, a colloidal delivery system, such as an oil-in-water emulsion, is often required to overcome these limitations (Boon et al., 2010). An oil-in-water emulsion consists of small lipid droplets (containing the lipophilic bioactive) suspended in an aqueous medium. This type of emulsion-based delivery system provides a suitable means of dispersing a lipophilic bioactive into the aqueous environments found in many commercial food products. In addition, the lipid phase breaks down within the human gastrointestinal tract to form colloidal structures (mixed micelles) that are capable of solubilizing and transporting the bioactive agents, thereby increasing their bioavailability (Nagao, 2014). Furthermore, emulsion-based delivery systems may also be designed to inhibit the rate of carotenoid degradation (Boon et al., 2010).
For commercial applications, it is important that any delivery system should remain physically and chemically stable when exposed to the different pH and temperature environments during its processing, storage, and transportation (McClements, 2005). The aim of this work was therefore to study the effect of temperature and pH on the physical and chemical stability of lutein-enriched emulsions. A natural protein-based emulsifier (caseinate) was used to stabilize the emulsions, and a source of long chain triacylglycerols (corn oil) was used as the lipid phase since this type of lipid has previously been shown to increase the bioaccessibility of carotenoids (Rao et al., 2013, Salvia-Trujillo et al., 2013).
Section snippets
Materials
MariLut Lutein, consisting of 20% (w/w) of lutein dissolved in corn oil, was kindly donated by PIVEG (San Diego, CA). Mazola corn oil was purchased from a local store. Spray dried sodium caseinate was purchased from the American Casein Company (Burlington, NJ). A lutein standard for chromatography analysis was purchased from Extrasynthese (Genay, France). Sodium azide and mono- and dibasic sodium phosphate were purchased from Sigma–Aldrich (St. Louis, MO, USA). Dimethyl sulfoxide (DMSO) was
Emulsion preparation
Emulsion-based delivery systems were prepared by homogenizing the organic and aqueous phases together to create a 10% w/w oil-in-water emulsion that contained 476 ± 22 mg of lutein per liter of emulsion. If this emulsion were diluted ten times to create a low-fat dairy-like beverage, then the amount of lutein per serving (240 mL) would be approximately 11.5 mg, which is higher than the recommended daily intake of lutein (10 mg) necessary to exert a beneficial effect on human health (Frede et al., 2014
Conclusions
This study has shown that it is possible to encapsulate lutein in emulsion-based delivery systems fabricated from all-natural ingredients (lutein, corn oil, and milk protein). These lutein-enriched emulsions can be used to create natural colorants or to fortify functional foods at a level that may be beneficial to human health. Elevated temperatures promoted rapid chemical degradation of lutein leading to color fading, and so it is important to avoid exposing the delivery systems to high
Acknowledgments
Dr. Gabriel Davidov-Pardo is recipient of a post-doctoral fellowship by the Secretaría de Ciencia Tecnología e Innovación del Distrito Federal (SECITI, Mexico City). This material is based upon work supported by the Cooperative State Research, Extension, Education Service, United State Department of Agriculture, Massachusetts Agricultural Experiment Station (Project No. 831) and by the United States Department of Agriculture, NRI Grants (2011-03539, 2013-03795, 2011-67021, and 2014-67021).
References (33)
- et al.
The science behind lutein
Toxicology Letters
(2004) Flocculation of protein-stabilized oil-in-water emulsions
Colloids and Surfaces B-Biointerfaces
(2010)- et al.
Stability and cellular uptake of lutein-loaded emulsions
Journal of Functional Foods
(2014) - et al.
Preparation of HIPEs with controlled droplet size containing lutein
Colloids and Surfaces A: Physicochemical and Engineering Aspects
(2014) - et al.
Thermal degradation kinetics of xanthophylls from blood orange in model and real food systems
Food Chemistry
(2013) - et al.
Stability and bioavailability of lutein ester supplements from Tagetes flower prepared under food processing conditions
Journal of Functional Foods
(2012) - et al.
Stability and loss kinetics of lutein and β-carotene encapsulated in freeze-dried emulsions with layered interface and trehalose as glass former
Food Research International
(2014) Theoretical prediction of emulsion color
Advances in Colloid and Interface Science
(2002)Protein-stabilized emulsions
Current Opinion in Colloid & Interface Science
(2004)- et al.
Structured emulsion-based delivery systems: Controlling the digestion and release of lipophilic food components
Advances in Colloid and Interface Science
(2010)
Physical and chemical stability of beta-carotene-enriched nanoemulsions: Influence of pH, ionic strength, temperature, and emulsifier type
Food Chemistry
Formation of nanoemulsions stabilized by model food-grade emulsifiers using high-pressure homogenization: Factors affecting particle size
Food Hydrocolloids
Influence of particle size on lipid digestion and beta-carotene bioaccessibility in emulsions and nanoemulsions
Food Chemistry
Dietary sources of lutein and zeaxanthin carotenoids and their role in eye health
Nutrients
Phase behavior, formation, and rheology of cubic phase and related gel emulsion in Tween80/water/oil systems
Journal of Oleo Science
Influence of layer thickness and composition of cross-linked multilayered oil-in-water emulsions on the release behavior of lutein
Food & Function
Cited by (83)
Multifunctional applications of natural colorants: Preservative, functional ingredient, and sports supplements
2024, Biocatalysis and Agricultural BiotechnologyDeveloping biopolymer-stabilized emulsions for improved stability and bioaccessibility of lutein
2024, International Journal of Biological Macromolecules